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' MOUND DESIGN WORK SHEET (For Flows up to 1200 gpd) <br /> A. Average Design FLOW A-1: Estimated Sewage Flows in Gallons per Day <br /> number of <br /> Estimated (000 gpd (see figure A-1) bedrooms Class I Class II Class Ill Class IV <br /> or measured -- x 1.5 (safety factor) = gpd 2 300 225 180 60% <br /> 3 450 300 218 of the <br /> 4 600 375 256 values <br /> B. SEPTIC TANK Capacity 5 750 450 294 in the <br /> 6 900 525 332 Class I, <br /> ?%' OO gallons (see figure C-1) 7 1050 600 370 ll,or III <br /> 100,0 ,4c '1-kvt- 41 4vrt• .,6 8 1200 675 408 columns. <br /> C. SOILS (refer to site evaluation) C-1: Septic Tank Capacities(in!allons) <br /> Number of Minimum Liquid Liquid capacity with Liquid sposal& <br /> Bedrooms Capacity disposal a 11h disposals <br /> 1. Depth to restricting layer = P.(613.�, �,la feet p garbagep lift inside <br /> 2. Depth of percolation tests = /,0 feet 2 or less 750 1125 1500 <br /> 3. Texture cLq L lc 'di3 or 4 1000 1500 2000 <br /> 5 or 6 1500 2250 3000 <br /> Percolation rate '6,0 mpi 7,8 or 9 2000 3000 4000 <br /> 4. Soil loading rate , .) ' gpd/sqft(see figure D-33) <br /> 5. Percent land slope 7 <br /> D.. ROCK LAYER DIMENSIONS <br /> 1. Multiply average design flow (A) by 0.83 to obtain required rock layer area. <br /> (o00 gpd x 0.83 sqft/gpd = 4-9 sqft+')via 98-17 ar <br /> 2. Determine rock layer width = 0.83 sqft/gpd x linear Loading Rate (LLR) <br /> 0.83 sqft/gpd x I a gpd/sqft = 10 ft Mound LLR —. <br /> 3. Length of rock layer = area -width = <br /> 54.1 sqft (D1) _ 10 ft (D2) = 5S ft < 120 MPI < 12 <br /> E. ROCK VOLUME > 120 MPI < 6 <br /> 1. Multiply rock area (Dl) by rock depth of 1 ft to get cubic feet of rock <br /> 549 sqft x 1 ft = <,`13'7 cuft <br /> 2. Divide cuft by 27 cuft/cuyd to get cubic yards <br /> 5 Y7 cuft _27 cuyd/cuft = w cuyd <br /> 3. Multiply cubic yards by 1.4 to get weight of rock in tons <br /> aG cuyd x 1.4 ton/cuyd = p,cG tons <br /> D-33: Absorption Width Sizing Table <br /> F. SEWAGE ABSORPTION WIDTH Percolation Rate Loading Rate <br /> in Minutes per Soil Texture Gallons Absorption <br /> Inch per day per Ratio <br /> (MPI) square Raft <br /> Faster than 5 Coarse Sand 1.20 1.00 <br /> Medium S <br /> Absorption width equals absorption ratio (See Figure D-33) LoamySan"d <br /> Fine Sand <br /> times rock layer width (D2) 6 to 15 Sandy Loam 0 79 150 <br /> 16 to 30 Loam 0.60 2.00 <br /> 31 to 45 Silt Loam 0.50 2.40 <br /> ''-,-V) X ft = "),kz,,r l ft46 to 60 Sandy Clay Loars 0.45 2.67 <br /> Silty Clay Loam <br /> Clay Loam <br /> 61 to 120 Silty Clay 0.24 5.00 <br /> Sandy Clay <br /> Clay <br /> Slower than 120• <br /> •Sysiein designed for these soils insist he oilier or iserlormaliss <br />